PCOL 838 Exam 1 2025/2026 Graded A+
Questions with 100% Correct Answers
gene - a segment of dna that encodes a pdt responsible for a
measurable trait
locus - location of a gene on a chromosome
allele - a variant form of a gene
mutation - a biochemical event such as a nucleotide change,
deletion, or insertion that has produced a new allele.
heterozygosity - Having two alleles at the same locus that
are diff erent.
Hemizygosity - A term referring to the presence of only one
allele at a locus, either because the other allele is deleted or
because it is normally not present, e.g., X-linked genes in
males.
polymorphism - an allele present in 1% or more of a
population;
,phenotype - any characteristic that can be measured, with
the type of measurement depending on the characteristic.
how can 2 individuals w/ the same mutation have the
different severity of disease - penetrance: manifestation of
disease phenotype under a set of predefined criteria (% of
people who inherit mutation and express associated trait)
Incomplete penetrance of dominantly inherited disease-
why deleterious allele persist in population
- Same mutation can affect different tissues-> different
phenotype-> variable expressivity
Explain the pathophysiologic difference between
mutations that act via loss of function and those that
act via dominant negative gene action -
Recessive loss of function mutation - autosomal, classical
Mendelian inheritance, only one allele is working, gives rise
to only 50% protein level, need both alleles to manifest
disease phenotype-> recessive inheritance
Dominant loss of function mutation - 50% protein level= not
enough for normal function->dominance inheritance. most
are semidominant w both loss of function alleles
manifesting more severe phenotype
, Dominant Negative Gene action - Involved in genes
encoding proteins involved in
oligomeric or polymeric protein complexes
Mutant protein disrupts the formation of normal
protein complexes->inhibiting normal function=dominant
inheritance
What are the different mode of inheritance - - depending on
locus of mutated gene. Autosomal vs X-linked. Autosomal
recessive or Dominant. X- linked dominant fragile X
syndrome) or recessive (hemophilia) mostly manifests in
men bec of hemizygosity. Codominance. Maternal
inheritance or matroclinous inheritance in mitochondria.
Leber hereditary optic neuropathy
(LHON - Mutations in genes located in the mitochondria
DNA.
•
Lead to optic cell death and progressive vision loss.
•
Incomplete penetrance: 50% of male and 85% of
female never experience any vision loss of related
health problems.
Questions with 100% Correct Answers
gene - a segment of dna that encodes a pdt responsible for a
measurable trait
locus - location of a gene on a chromosome
allele - a variant form of a gene
mutation - a biochemical event such as a nucleotide change,
deletion, or insertion that has produced a new allele.
heterozygosity - Having two alleles at the same locus that
are diff erent.
Hemizygosity - A term referring to the presence of only one
allele at a locus, either because the other allele is deleted or
because it is normally not present, e.g., X-linked genes in
males.
polymorphism - an allele present in 1% or more of a
population;
,phenotype - any characteristic that can be measured, with
the type of measurement depending on the characteristic.
how can 2 individuals w/ the same mutation have the
different severity of disease - penetrance: manifestation of
disease phenotype under a set of predefined criteria (% of
people who inherit mutation and express associated trait)
Incomplete penetrance of dominantly inherited disease-
why deleterious allele persist in population
- Same mutation can affect different tissues-> different
phenotype-> variable expressivity
Explain the pathophysiologic difference between
mutations that act via loss of function and those that
act via dominant negative gene action -
Recessive loss of function mutation - autosomal, classical
Mendelian inheritance, only one allele is working, gives rise
to only 50% protein level, need both alleles to manifest
disease phenotype-> recessive inheritance
Dominant loss of function mutation - 50% protein level= not
enough for normal function->dominance inheritance. most
are semidominant w both loss of function alleles
manifesting more severe phenotype
, Dominant Negative Gene action - Involved in genes
encoding proteins involved in
oligomeric or polymeric protein complexes
Mutant protein disrupts the formation of normal
protein complexes->inhibiting normal function=dominant
inheritance
What are the different mode of inheritance - - depending on
locus of mutated gene. Autosomal vs X-linked. Autosomal
recessive or Dominant. X- linked dominant fragile X
syndrome) or recessive (hemophilia) mostly manifests in
men bec of hemizygosity. Codominance. Maternal
inheritance or matroclinous inheritance in mitochondria.
Leber hereditary optic neuropathy
(LHON - Mutations in genes located in the mitochondria
DNA.
•
Lead to optic cell death and progressive vision loss.
•
Incomplete penetrance: 50% of male and 85% of
female never experience any vision loss of related
health problems.
